The present invention relates to a coil arrangement for a nuclear fusion apparatus, and more particularly it relates a transition-feeder structure of the coil arrangement for a nuclear fusion apparatus.
A convention coil arrangement for a nuclear fusion apparatus is constructed as shown in FIGS. 1 and 2. In the figures, reference numeral 1 designates a coil conductor, numeral 2 a transition conductor between turns, numeral 3 a transition conductor between coil layers, and numeral 4 a feeder line.
A current flows through the coil conductor 1, but when it flows through the transition conductor between turns 2, transition conductor between coil layers 3 and feeder line 4, additional current components other than the current which flows through the coil conductor 1 are generated, since they are deviated from the direction of the arc of the coil. The additional current components generate error magnetic fields which are harmful in that they effect the confinement of plasma within the coil. It is clear that the smaller the loop area of the extra currents is, the smaller the error magnetic field becomes. It has been therefore conceived that the transition structure be changed.
FIG. 3 is a schematic diagram showing the mode of transition of the current flowing through the coil. In the figure, reference numeral 5 designates arrow indicating the direction of the current flowing through the coil, numeral 6 a transition current between coil layers, numeral 7 a transition current between coils, and numeral 8 a return conductor. As can be seen from the figure, the transition directions are reversed to each other as indicated by the arrow 6, so as to minimize the error magnetic field in the inner side of the coil in the vicinity of the plasma (not shown).
However, even with the conventional technique as shown in FIG. 3, there exists the possibility of the problem that current loops may remain and generate the error magnetic fields, since the error magnetic fields may not be cancelled out sufficiently. Furthermore, there exists the problem in the production of the coil arrangement due to the fact that the mode of transition between coil layers is complicated.